Update Travis CI config, add AppVeyor for Windows CI coverage.

appveyor.yml

@@ -0,0 +1,38 @@
+# Build matrix / environment variables are explained on:
+# https://www.appveyor.com/docs/appveyor-yml/
+# This file can be validated on: https://ci.appveyor.com/tools/validate-yaml
+
+version: "{build}"
+
+environment:
+  matrix:
+    # AppVeyor currently has no custom job name feature.
+    # http://help.appveyor.com/discussions/questions/1623-can-i-provide-a-friendly-name-for-jobs
+    - JOB: Visual Studio 2017
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      CMAKE_GENERATOR: Visual Studio 15 2017
+    - JOB: Visual Studio 2015
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      CMAKE_GENERATOR: Visual Studio 14 2015
+
+platform:
+  - x86
+  - x64
+
+configuration:
+  - RelWithDebInfo
+  - Debug
+
+build:
+  verbosity: minimal
+
+build_script:
+  - git submodule update --init --recursive
+  - mkdir out
+  - cd out
+  - cmake .. -G "%CMAKE_GENERATOR%"
+      -DCMAKE_CONFIGURATION_TYPES="Debug;RelWithDebInfo"
+  - cmake --build . --config %CONFIGURATION%
+
+test_script:
+  - ctest -C %CONFIGURATION% --output-on-failure